1. Field of the Invention
The present invention relates to an ink-jet printhead and a method of manufacturing the ink-jet printhead, and more particularly, to an ink-jet printhead having an improved structure preventing deformation of a nozzle plate, filtering out impurities remaining in ink, and preventing a head chip from being damaged by cracks, and a method of manufacturing the ink-jet printhead.
2. Description of the Related Art
In general, ink-jet printheads are devices for printing a predetermined color image by ejecting small volumes of droplets of printing ink at desired positions on a recording sheet. These ink-jet printheads are divided by two driving methods according to an ink ejection mechanism: ink-jet printheads using a thermal driving method of ejecting ink droplets by an expansion force of bubbles generated in ink by a heat source, and ink-jet printheads using a piezoelectric driving method of ejecting the ink droplets by a pressure applied to the ink due to deformation of a piezoelectric body.
Hereinafter, the ink ejection mechanism in the thermal ink-jet printheads will be described in greater detail. When current having a pulse shape flows through a heater formed of a resistance heating material, heat is generated in the heater, and the ink adjacent to the heater is instantaneously heated to about 300° C. As such, ink is boiled, and the bubbles are generated in the ink, expand, and apply the pressure to an inside of an ink chamber filled with the ink. As a result, the ink in the vicinity of a nozzle is ejected in a droplet shape through nozzles of the ink chamber.
Here, the thermal driving method includes a top-shooting method, a side-shooting method, and a back-shooting method according to a growth direction of the bubbles and an ejection direction of the ink droplets.
The top-shooting method is a method in which the growth direction of the bubbles is the same as the ejection direction of the ink droplets. The side-shooting method is a method in which the growth direction of the bubbles is perpendicular to the ejection direction of the ink droplets. The back-shooting method is a method in which the growth direction of the bubbles is opposite to the ejection direction of the ink droplets.
The ink-jet printheads using the thermal driving method should satisfy the following requirements. First, manufacturing of the ink-jet printheads has to be simple, costs have to be low, and mass a production thereof has to be possible. Second, in order to obtain a high-quality image, a crosstalk between adjacent nozzles has to be suppressed and an interval therebetween has to be narrow, that is, in order to increase the number of dots per inch (DPI), a plurality of nozzles has to be arranged with narrow intervals therebetween. Third, in order to perform a high-speed printing operation, a period in which the ink chamber is refilled with ink after the ink is ejected from the ink chamber, has to be as short as possible, and heated ink has to be quickly cooled such that a driving frequency can increase.
FIGS. 1A and 1B show a conventional ink-jet printhead using a thermal driving method. FIG. 1A is a sectional perspective view of a structure of the conventional ink-jet printhead, and FIG. 1B is a cross-sectional view illustrating operations of ejecting ink droplets in the conventional ink-jet printhead, disclosed in U.S. Pat. No. 4,882,595. Referring to FIGS. 1A and 1B, the conventional ink-jet printhead using the thermal driving method includes a substrate 10, a barrier wall 14 which is formed on the substrate 10 and defines an ink chamber 26 and an ink channel 24, a heater 12 installed under the ink chamber 26, and a nozzle plate 18 having a nozzle 16 through which ink droplets 29′ are ejected. When a current having a pulse shape is supplied to the heater 12 and heat is generated from the heater 12, ink 29 filled in the ink chamber 26 is heated, thereby generating bubbles 28 in the ink 29. The bubbles 28 expand continuously such that a pressure is applied to the ink 29 filled in the ink chamber 26 and the ink droplets 29′ are ejected through the nozzle 16 to an outside of the ink-jet printhead. Subsequently, the ink 29 is supplied to the ink chamber 26 through the ink channel 24 from a manifold 22, and the ink chamber 26 is refilled with the ink 29.
However, in the above conventional ink-jet printhead, the ink channel 24 or the nozzle 16 is clogged with impurities remaining in the ink 29 such that the ink 29 is not well supplied to the ink channel 24 or the nozzle 16. Also, cracks occur at both sides of a surface of the substrate 10 in which the manifold 22 is formed, such that a head chip of the ink-jet printhead may be damaged. Meanwhile, since the ink-jet printhead as described above is manufactured by attaching the nozzle plate 18 to the substrate 10, a process of manufacturing the ink-jet printhead becomes complicated, and a misalignment may occur during the attaching process.
FIG. 2 shows another conventional ink-jet printhead proposed to solve the above problems and is a sectional perspective view of a structure of the conventional ink-jet printhead disclosed in U.S. Pat. No. 5,912,685. Referring to FIG. 2, the ink-jet printhead includes a substrate 1, a barrier wall 2 which is formed on the substrate 1, a barrier layer 3 which defines an ink channel 7 together with the barrier wall 2, a heater 4 installed under an ink chamber 9, and a nozzle plate 5 in which a nozzle 6 is formed. In the above structure, ink is sent into the ink chamber 9 through the ink channel 7 formed by the barrier wall 2 and the barrier layer 3 from a manifold 8. Thus, ink of which impurities are filtered out is supplied to the ink chamber 9.
However, in the above ink-jet printhead, when a large amount of the impurities remain in the ink, the ink channel 7 is clogged with the impurities such that the ink cannot be supplied any longer to the ink chamber 9. Meanwhile, as described above, cracks may occur at both sides of a surface of the substrate 1 in which the manifold 8 is formed, and a process of manufacturing the ink-jet printhead becomes complicated.